This disclosure relates generally to the field of optical scanners. More specifically, the disclosure relates to a system, method, and apparatus for accurately and repeatably scanning an object with a scanner, such as an optical scanner, wherein an object to be scanned is fixed positionally relative to a reference pattern.
In a specific embodiment, a system, method, and apparatus in accordance with this disclosure relates to intra-oral scanning of a patient's dentition in connection with the prosthodontic and orthodontic treatment of dental conditions such as mal-alignment of dentition and the replacement of missing teeth. In accordance with this embodiment, this disclosure relates to an apparatus, system, and method for intra-oral scanning of a patient's dentition for providing a course of treatment for such conditions, and, in a specific embodiment, for providing a series of appliances that would implement the course of treatment.
Optical scanning of a three-dimensional object typically involves the use of an optical scanner that obtains and renders a digitized 3-D image of the object. The typical optical scanner employs a scanner head that takes a series of individual 3-D images of predetermined segments of the object, segment-by-segment, in either a predetermined or user-directed sequence. The scanner employs software that digitizes the segment images and then “stitches” them together to render a composite 3-D image of the entire object (or at least the portion of the object for which a composite image is desired). Thus, in cases where the object is larger than a single segment image, multiple segment images are required to render the desired composite image.
A problem may arise, however, in cases where the object has one or more “smooth” surfaces, i.e., surfaces having few, if any, distinctive features, or surfaces having gradual (non-abrupt) shape transitions. In such situations, each segment image may fit along a large number of orientations relative to an actual desired placement or position within the object as a whole. In other words, if the entire object is considered to be a completed mosaic made of individual segment images, each segment image may be likened to an individual mosaic piece. Where the completed mosaic is relatively featureless, it may be difficult, if not impossible, to determine exactly where, in the completed mosaic, each individual piece is located and how it is oriented with respect to other mosaic pieces. Therefore, it would be desirable to provide some way to provide a reference pattern that may be scanned along with the object, so that each segment image will include a corresponding reference image that provides a fixed registration for the segment image for determining a location and orientation for the segment image relative to the other segment images that constitute the desired composite image.
One specific application of optical scanning is intra-oral scanning of a patient's dentition. Intra-oral scanning typically involves the use of an optical scanner that obtains a digitized 3-D image of a patient's dentition without the need for making a physical model, such as a casting or “stone” of an impression of a patient's dental arch. While dental arches typically have sufficient surface features to avoid (or at least to minimize to a manageable degree) the above-noted problems with relatively featureless objects, the use of a registration mechanism to provide a segment image that includes a reference image would likely result in faster image-generation speeds with respect to the rendering of a computer-generated composite image of the entire dental arch. Moreover, there are cases, such as scanning an edentulous (toothless) arch (for, e.g., the fitting of dentures), in which the problems of scanning a relatively featureless object may be present to varying degrees. Furthermore, in creating a treatment plan or course of treatment for a prosthodontic or orthodontic treatment of a patient, it is typically necessary or desirable to take an intra-oral scan of one or both of the patient's dental arches before beginning the treatment plan, and then to take one or more subsequent scans at various stages during the course of treatment, or at least after the course of treatment has been completed. In such cases, it would be desirable to assure that the pre-treatment scan and all subsequent treatment scans are taken with respect to the same fixed reference frame, so that the position of the dentition in the scanned dental arch at a time TN may quickly and accurately be determined relative to the position of the dentition at an earlier time, for example a pre-treatment time T0.